Propelling transmission system of tractor

Abstract

A propelling transmission system of a tractor comprising a front transmission for driving front wheels and a rear transmission for driving rear wheels. The front transmission receives drive from an engine mounted at a front position of the tractor, through a main clutch housed in a clutch case, and transmits the drive to the rear transmission. The rear transmission returns part of the drive to a front wheel change speed mechanism included in the front transmission. The front transmission is housed in a front transmission case directly connected to a lower rearward position of the clutch case.

What is claimed is: 
     
       1. A propelling transmission system of a tractor comprising; a main transmission mechanism including an input shaft for receiving, through a main clutch mechanism, drive from an engine mounted at a front position of the tractor, and a first transmission shaft disposed parallel to the input shaft and operatively connected thereto,   a rear transmission disposed at a rear position of the tractor for receiving the drive from the first transmission shaft,   front wheel drive means including a second transmission shaft disposed parallel to the first transmission shaft and receiving the drive from the rear transmission,   front wheel change speed means for receiving the drive from the second transmission shaft and transmitting the drive to front wheels selectively in a standard drive mode for driving the front wheels substantially at the same speed as the rear wheels and in a high speed mode for driving the front wheels at a higher speed than the rear wheels, and   a front transmission case housing the main transmission mechanism, front wheel drive means and front wheel change speed means, the front transmission case being directly connected to a lower rearward position of a main clutch case.   
     
     
       2. A propelling transmission system as claimed in claim 1, wherein the front wheel change speed means is disposed downwardly of a clutch sleeve for connecting and disconnecting the main clutch mechanism to/from the input shaft. 
     
     
       3. A propelling transmission system as claimed in claim 1, wherein the input shaft and the first transmission shaft are operatively connected to each other by gearing. 
     
     
       4. A propelling transmission system as claimed in any one of claims 1 to 3, wherein the front wheel change speed means includes a relay member relatively rotatably mounted on the first transmission shaft and including a pair of gears,   a third transmission shaft disposed coaxially with the second transmission shaft, and   a clutch mechanism mounted on the third transmission shaft for selecting between a first transmission mode in which the drive is transmitted without change speed from the second transmission shaft to the third transmission shaft and a second transmission mode in which the drive is transmitted from the second transmission shaft to the third transmission shaft through the relay member for effecting change speed.   
     
     
       5. A propelling transmission system as claimed in claim 4, wherein the third transmission shaft is connected through an accelerating means to a fourth transmission shaft operatively connected to the front wheels. 
     
     
       6. A propelling transmission system as claimed in claim 1, further comprising a steering gear box supporting a pitman arm, and a mechanical linkage connecting the pitman arm to the front wheel change speed means for switching the front wheel change speed means to the high speed mode in response to a steering operation exceeding a predetermined amount, the steering gear box being disposed adjacent the engine. 
     
     
       7. A propelling transmission system as claimed in claim 6, wherein the steering gear box is directly connected to a top surface of the front transmission case. 
     
     
       8. A propelling transmission system of a tractor comprising; an engine mounted at a front position of the tractor,   a rear transmission disposed at a rear position of the tractor,   a main transmission mechanism for receiving drive from the engine through a main clutch mechanism, and transmitting the drive to the rear transmission,   front wheel drive means for receiving the drive from the rear transmission,   front wheel change speed means for receiving the drive from the front wheel drive means and transmitting the drive to accelerating means operatively connected to front wheels, the front wheel change speed means being contained in a position downwardly of a clutch sleeve for operating the main clutch mechanism, and   a front transmission case housing the main transmission mechanism, front wheel drive means and front wheel change speed means, the front transmission case being directly connected to a lower rearward position of a main clutch case.